Research Of Heterogeneous Fe₂O₃in Activation Of Peroxymonosulfate For Decolorization Of Rhodamine B

Advanced Oxidation Technologies based on the sulfate radicals have attracted wideattentions in recent years. Sulfate radicals have a higher redox potential than hydroxylradicals, which show a strong oxidizing ability. Currently in the research of persulfateactivation, all the methods have advantages and disadvantages. Among them,heterogeneous catalysis of the transition metal oxide causes concern for its safety andefficiency.Iron trioxide catalysts were prepared by two different methods in this paper. Thedegradation effects of Rhodamine B (RhB) were investigated in heterogeneousFe2O3/PMS system when PMS was used as oxidant. Meanwhile the preparationconditions of Fe2O3and reaction conditions of reaction system on the degradation ofRhB were discussed respectively. The causes of the differences of catalytic effect fortwo different methods are discussed.Iron trioxide catalysts were prepared by sol-gel method and characterized byX-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). We firstlyintroduced the Fe2O3to the reaction system in presence of PMS to remove the RhB. Thedegradation efficiency of RhB was66.97%, and removal rate of Total Organic Carbon(TOC) was51.24%in60min, which showed that Fe2O3had a good catalyticperformance. The preparation conditions of Fe2O3on the effect of RhB degradationwere studied, and the removal conditions for the preparation of Fe2O3were as follows:the calcination time was5h, calcination temperature was600℃and hydrothermaltime was6h. The effects of reaction conditions on degradation effect of RhB had beeninvestigated. When the conditions were as follows: at room temperature, pH was7, theconcentration of RhB was50mg/L, PMS was1.0mmol/L and Fe2O3was2.1g/L, thedegradation efficiency was87%in60min, which indicated that Fe2O3/PMS systempossessed a good efficiency for RhB removal.Another iron trioxide catalyst was prepared by glycine hydrothermal method andalso characterized by XRD and SEM. The degradation experiments of RhB were carriedout with PMS as oxidant and Fe2O3as catalyst. The degradation efficiency of RhBcould reach to100%and removal rate of TOC was77.86%in60min, which showedthat Fe2O3produced by glycine hydrothermal method exhibited a great catalyticperformance. The various influence various parameters such as preparation conditionsof Fe2O3and reaction conditions had been studied. It was found that the dosage ofglycine was2g, hydrothermal temperature was160℃, hydrothermal time was10h,calcine temperature was450℃, and calcine time was3h. The results showed thatmaximum removal of RhB took place when pH was7, the concentration of RhB was50mg/L, PMS was1.0mmol/L and Fe2O3was1.5g/L at room temperature. The degradation efficiency of phenol was100%, which indicated that Fe2O3/PMS system isvery effective for RhB removal. The reaction quenching studies with Methanol (MeOH)and Tert Butyl Alcohol (TBA) showed that there were both SO4· and OH·in thereaction system. We establish apparent kinetic equation of RhB by changing the reactiontemperature, and find the reaction is first order kinetic equation.The reusability of two different Fe2O3catalysts for RhB degradation had beeninvestigated. The catalysts were reused for five and four times respectively. Thedegradation efficiency of RhB was still maintained high efficiency for the Fe2O3madeby sol-gel method and glycine hydrothermal method respectively. By measuring thespecific surface area and total pore volume determination, special preparation methodswill generate more porous crystalline and bigger surface area for iron trioxide. That wasthe main difference in their catalytic performance.